The present invention relates to fasteners and more particularly, relates to a plastic encapsulated bolt and a plastic anchor for use therewith.
Structural anchors are commonly used to secure or anchor a structural device to a substrate, such as concrete. Structural anchors typically include an internally threaded insert positioned within the concrete or other substrate and an externally threaded bolt that threadably engages the insert. Although such structural anchors are useful in a number of different industries, certain industries, such as rail transportation, telecommunications and water and sewage treatment, require structural anchoring systems that are both non-conductive and non-corrosive.
The serious problems resulting from corrosion in rail systems are discussed in xe2x80x9cStray Current Corrosionxe2x80x9d, a publication by NACE (National Association of Corrosion Engineers) International.
Existing plastic female anchors, such as the type disclosed in U.S. Pat. Nos. 5,490,750 and 5,641,256, provide effective resistance to conductivity and corrosion. When used with a metallic bolt, however, conductivity and/or corrosion may still be a problem. Existing reinforced plastic bolts might provide resistance to conductivity and corrosion but are not suitable for use in high-strength situations. Epoxy coated fasteners have also been used in an attempt to prevent corrosion, but a hole in the epoxy layer can result in centralized corrosion and a quicker failure than even uncoated metal fasteners.
Accordingly, a need exists for a plastic encapsulated bolt that is non-conductive and non-corrosive and that can be used in high-strength situations. There is also a need for a structural anchoring system that is non-conductive and non-corrosive and that can be used in various industries.
The present invention features a plastic encapsulated bolt comprising an insert made of metallic material and having a head and a shank. An outer plastic layer encapsulates the insert and forms a plastic encapsulated head and a plastic encapsulated shank. The plastic encapsulated shank includes an externally threaded portion on at least part of a length thereof. The insert can be either a threaded bolt or a bolt blank and, in one example, is made of steel.
The present invention also features a combination bolt and anchor assembly comprising a plastic encapsulated bolt and a plastic female anchor having an internally threaded portion for receiving the plastic encapsulated bolt.
In one embodiment, the plastic encapsulated shank has a tapered threaded nose and the plastic female anchor includes at least two longitudinal slots. The internally threaded portion of the plastic female anchor includes an undersized thread diameter such that the tapered nose of the plastic encapsulated bolt engages the undersized threads and the plastic female insert expands as the plastic encapsulated bolt is threaded therein.